Optical communication management systems

ABSTRACT

An optical medium, whether inside or outside an internet/telecommunications backbone, is managed using a management signal at a wavelength which is distinct from wavelengths of service signals. A multiplexer multiplexes the management signal onto the optical medium, after which a demultiplexer demultiplexes the management signal for analysis. Performance of customer channels may be inferred from performance of the management signal.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/400,164, filed Mar. 25, 2003, which claims the benefit of U.S.Provisional Application No. 60/368,784, filed on Mar. 28, 2002. Theentire teachings of the above applications are incorporated herein byreference.

BACKGROUND OF THE INVENTION

A telecommunications network can be viewed as consisting of three mainsections: the backbone network, the metro network and the accessnetwork. The backbone network connects major switching centers typicallylocated in major cities. The metro network connects a backbone switchingcenter to smaller switching centers located within a metropolitan area,i.e. within a city. The access network connects end user customers tothe switching centers of the metro network.

In the backbone the traffic of tens of thousands to millions ofcustomers is aggregated (multiplexed) onto the optical transportequipment that forms the interconnections between switching centers. Thecost per customer traffic flow is therefore low due to the amortizationof the high equipment costs across the large number of flows. The metronetwork carries the traffic of hundreds to thousands of customers. Thecost per customer flow is higher than in the backbone because the costof the transport equipment is amortized over a smaller number of flows.The access network connects a very small number of customers or often asingle customer to the metro switching centers. The transport equipmentused to make these customer connections is typically the same as thatused in the metro network. The cost of the access transport is thusamortized over a small number or single customer traffic flow.

The dominant optical transport technology is Synchronous OpticalNetworking (SONET) in North America, or Synchronous Digital Hierarchy(SDH) elsewhere. The service providers who operate these networks haveoperational support systems (OSS) that are used to provision, monitor,diagnose and control their transport network. These OSS systems range insize or complexity dependant upon the operators environment, rangingfrom individual element manager systems addressing one or more of themajor management disciplines—Fault, Configuration, Accounting,Performance, Security —(FCAPS), to highly integrated systems providingtight coupling and interdependence across these roles. These OSS systemsare designed to use familiar, consistent data retrieved and recordedfrom the transport network, predominantly based on standard SONET/SDHmetrics. Equipment that does not provide performance data in the formatsrequired by these OSS, and hence does not readily integrate, representsan added cost to the service providers.

SUMMARY OF THE INVENTION

The systems described herein address both the capital costs (CAPEX) andthe operational costs (OPEX) of provisioning optically based services tothose enterprise (business) customers that require sufficient bandwidthto require optical fiber connections.

Costs of providing optically delivered services to enterprise customerscan be reduced; i) by separating the optical transport function from theoptical service being delivered over the optical medium; ii) bysimplifying the optical transport equipment required at the centraloffice (CO) and at the customer premise; and iii) by interfacing to theOSS systems in the same way as the existing transport equipment.

Additional operational functionality which may also be provided include;i) the ability to provide loopback testing of the optical connectionwithout interrupting the service delivery; ii) the ability tocontinuously (or intermittently) monitor the optical connection andraise an alarm if the connection is compromised by unwelcomeinterdiction; iii) the ability to establish a communications channelacross the medium separate from the optical channel carrying theservice; and iv) the ability to establish a management control planeacross any topology.

The disclosed system can operate in a variety of different networktopologies such as; i) point to point direct connections, ii) complexmesh networks, and iii) ring networks.

Optical fiber facilities delivering communications services may bemanaged and monitored using an optical medium management signal (OMMS)at a wavelength which is distinct from wavelengths used for the deliveryof services. An optical multiplexer multiplexes the OMMS onto theoptical medium with the customers' optical service signal. After theOMMS traverses the optical medium, a demultiplexer removes the OMMS fordemodulation and processing. Availability, performance and otheroperational metrics of the communications service wavelengths across theoptical medium may be inferred from the operation, availability andperformance of the OMMS carried on the management wavelength. Forexample, if the OMMS detects a large number of errors after passingthrough the optical medium, it may be an indication of problems with themedium and may be taken to indicate a large number of errors in servicesignals as well.

The OMMS is sent out across the optical medium by an optical jack at oneend of an optical medium, and is also received by an optical jack,whether the same one, or an optical jack at another point on the opticalmedium. The use of optical jack system is not limited to a single fiberor a two fiber connection. Optical jacks may be used anywhere in ageneral network topology, interacting with each other and with overallnetwork management services. Typically, although not exclusively, pairsof fiber optic strands are the preferred method for delivery of opticalservices, with one fiber acting as a transmit medium and the other as areceive medium. In this embodiment each optical demarcation jack on theoptical span might provide both the modulation and multiplexing of anOMMS onto one fiber and the demultiplexing and demodulation of an OMMSfrom the other fiber, providing management and monitoring of both fiberstrands. Alternatively, a single fiber broadcast service where only atransmit fiber is provided between end points could be envisioned. Inthis embodiment each optical jack might either provide both modulationand multiplexing of the OMMS onto the fiber, or the demultiplexing anddemodulation of an OMMS at the other end of the single fiber

Typical service signals used in optical fiber transmission are in one ofthe three distinct wavebands: Nominally 850 nm, 1200 nm-1400 nm and 1470nm-1610 nm. The OMMS may be in a different waveband from the servicesignals. Alternatively, the OMMS may be in the same waveband as theservice signals to better reflect the quality of service delivered inthat waveband. The wavelength of the OMMS may be fixed within the designof the optical jack, or the optical jack may have optical componentscapable of being set to generate and multiplex signals at differentwavelengths.

The protocol carried on the OMMS may provide detailed performancemetrics such as, but not exclusively, received signal strength, quality,framing status, error rates, CRC errors, transmission block errors andother media and protocol specific metrics which are relevant to thestate and performance of the optical medium.

In the majority of current optical network connections SONET(Synchronous Optical Network), and its international equivalent SDH(Synchronous Digital Hierarchy), (Sonet/SDH) line protocols provide astructured set of alarms, status and performance metrics relating tooptical line systems that are well known and understood by networkoperations personnel and tightly integrated into the OSS. In thepreferred embodiment, a standard SONET/SDH formatted optical mediummanagement signal, modulated and multiplexed onto the optical medium, isused, providing a consistent set of known and understood metricsrelevant to the optical medium independent of the format or protocols ofthe delivered service across that optical medium. In alternativeembodiments other standard or proprietary optical line protocols may beused to achieve the same or similar capabilities as required or definedby the OSS environment.

The OMMS protocol will typically include a payload, or allocated bytesand/or bits within the defined protocol structure for end to end datacommunications. Where this communications capability exists within theOMMS it may be used to provide inter unit communications betweenprocessors and applications running on the optical demarcation jacksacross the optical medium. This communication path between optical jacksmay be used to provide an operational management and control plane,enabling any applications running on individual optical jacks to beaccessed and controlled from any point in the network and for managementinformation to be exchanged from any optical jack to another or to anyhigher order OSS.

Typically the OMMS will be multiplexed across the optical medium withthe same directionality as the optical service, i.e. both multiplexedsignals traverse the optical medium in the same direction. Foradditional diagnosis, the OMMS may be driven in opposite direction tothe optical service signals.

In some situations an optical jack may be instructed to attenuate theoptical medium management signal. The attenuation may be accomplished byreducing the optical launch power of the optical transmitter or by usingan optical attenuator prior to the OMMS being multiplexed onto theoptical medium. The OMMS is attenuated independent of the servicesignals to operate near or at a level where further attenuation orimpairments of the optical medium end to end would significantly impactthe errors incurred in demodulation and hence measured by the receivingoptical jack.

A forward error correcting protocol may also be implemented across theOMMS path between optical jacks to ensure that end to end communicationscan be maintained even though the optical path is incurring errors. Theerror correction protocol would provide additional managementinformation relative to error counts to complement those metricsavailable from the error detection inherent in the optical mediummanagement signal. These modes of operation provide greater sensitivityto changes in the optical characteristics of the optical medium.

Management information on performance, errors, alarms, status,diagnostics etc., generated in a known and understood form from theoptical jack local processing or collected remotely from other opticaljacks, may then be recorded in a database located at the optical jack orforwarded to a optical jack control shelf where additional storage,processing and forwarding of relevant information to higher ordernetwork management or operational support systems can be completed. Byrecording and processing performance statistics in these databases, itis possible to identify trends and anomalies and predict futureperformance of the optical medium and the transported optical services,pre-emptively anticipating service affecting problems.

The optical demarcation jack may include external interfaces to provideoperationally important functions to remote locations for items such asmonitoring or activating NC/NO contacts, reporting remote batteryvoltages, temperature, humidity or access alarms, or providing remoteequipment management and remote technician Ethernet access, etc. Acommunications network overlaid on the OMMS communications paths may beused to communicate such site-specific information from one place toanother over a management and control plane established on this network.

Typically, managing the optical medium using the OMMS does not affectthe service signals at all, and the service is uninterrupted. However,in an alternative embodiment of the invention, the optical jack may alsoinclude programmable components, monitoring and analyzing specificservices transmitted on service signals.

In general, the optical jack system may be used to manage optical mediadelivering service connections, as well as to light up “dark fiber”,that is, to manage fiber currently not carrying service signals onbehalf of the owner of the fiber facility, but made available to otherparties to pass their own signals from one point to another in anetwork. The agnostic qualities of the optical demarcation point henceallow any format signal to be passed with no service specificrequirements on the owner of the facility but with the ability toprovide management, and if required, pro-active support services to theusers of the facilities.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1 is schematic diagram of a general optical networking environment.

FIG. 2 is a diagram of networking between a control jack and ademarcation jack.

FIGS. 3 a and 3 b are diagrams of different implementations ofdemarcation jacks.

FIG. 4 is a diagram of a single fiber network connection with managementand analysis electronics at the demarcation jack.

FIG. 5 is a diagram of two fiber network connection with a passivedemarcation jack.

FIG. 6 is a diagram of a two fiber network connection with an amplifierat the demarcation jack.

FIG. 7 is a diagram of a two fiber network connection with managementand analysis electronics at the demarcation jack.

FIG. 8 is a diagram of a two fiber network connection with remotemanagement information interface.

FIG. 9 is a diagram of a two fiber network connection with test accesspoints.

FIG. 10 is a diagram of a two fiber network connection with a serviceemulator.

FIG. 11 is a schematic diagram of one network topology.

FIG. 12 is a diagram of an optical loop network with tunable opticalmultiplexers and transceivers.

FIGS. 13 a-13 b are schematic representations of wave divisionmultiplexing.

FIG. 14 is a diagram of an optical jack networking system.

FIG. 15 is a graph of optical power vs. bit error rate of an opticalsignal.

DETAILED DESCRIPTION OF THE INVENTION

A description of preferred embodiments of the invention follows.

FIG. 1 is a schematic diagram of a general optical networkingenvironment. Backbone network 50 is a web of tightly coupledpredominantly fiber-based networks, with well-orchestrated points ofhand-off between various backbone providers, telecommunicationcompanies, and other parties. The operation of backbone network 50 istypically overseen by Operation Support Systems (OSS) 102, providingvisibility into the network for Network Operation Centers (NOC's),central office (CO) technicians, and a range of planning and businessprocesses requiring status and use of information relating to thenetwork. The OSS in support of NOC's within operational networks aretypically mission-critical, in that they are required to provideresponses within minutes or even seconds of a network interruption. Suchresponse may include re-routing or cutting back on traffic, attemptingrepair of the faulty point, or at least reporting the fault to partiesresponsible for fixing the point of failure. Other OSS, although notcritical to maintaining the integrity of the network, are as equallyimportant to be updated for any changes that may happen, such asaccounting systems administrating service level agreements whereavailability or error free performance of a service over time is a keymetric to be applied. The systems are well-tested and require minimumdown-time, and, while they may not be the state of the art in terms oftechnical specifications, they provide a tightly woven infrastructure tooperate and administer networks and their facilities. Hence,telecommunication companies would generally prefer to maintain thesesystems for most of the fiber based services, rather than to have toinvest in separate management and maintenance system for each serviceprovided.

Network performance is measured in a variety of schemes, defined bystandards, whether general, or proprietary. Synchronous Optical Network(SONET) is one such standard for optical telecommunications transportand management. Synchronous Digital Hierarchy (SDH) is a counterpartstandard to SONET used outside of North America. SONET/SDH performanceand availability metrics may be used to measure and analyze performanceof optical connections, and most established OSS systems are usuallywell-adapted to work with such metrics in the backbone and accessnetworks.

Optical service providers may prefer to retain control over customeraccess loops 120 a-x in order to be able to detect and diagnose pointsof failure, as well as to be able to correctly bill and administerSLA's. If visibility and control over customer access lines isunavailable due to deployment of transport systems incompatible with OSSor even completely lacking any management capabilities, optical serviceproviders may experience a so-called “black hole” problem, whereperformance impairments of the fiber optic access line are not reported,discovered or diagnosed promptly by the service provider's OSS. Forexample, in the case of a broken fiber in an unmanaged access loop, theservice provider would not be able to diagnose it accurately because, tothe service provider, the situation would be indistinguishable from onewhere the customer equipment is faulty. Meanwhile, the customer wouldnot have resources to diagnose or repair the failure because thecustomer would not have physical control of the fiber, and because tothem the situation might be indistinguishable from a fault on theservice provider side. The usual response to this situation is a costly‘truck roll’ with a field technician dispatched to test and confirm theintegrity and performance of the fiber facility to the customerlocation. Typically, this situation is unacceptable to all serviceproviders and most customers who expect prompt, if not predictive,detection of problems and rapid restoration of service.

Therefore, the service provider needs to retain control over thecustomer end of the fiber in order to maintain and manage the accessline. A point where the service provider hands off responsibility to thecustomer is called a demarcation point. Any failure beyond thedemarcation point is the customer's responsibility, while the serviceprovider is responsible for the connection up to the demarcation point.By positioning equipment controlled by the service provider at thedemarcation point, the service provider retains control over bothtransmit and receive fibers and the centrally located (NOC or CO)service provider technicians can access the equipment for monitoring anddiagnostics in cases of failure. Typically, a customer might call in toreport a problem, and a technician may attempt to send instructions tothe demarcation point equipment. If the equipment replies with properresponses, the technician may conclude that the problem is, indeed, onthe customer end. If, however, the results of the test instructions donot comply with what is expected, the service provider retains theresponsibility of fixing the connection.

Another consideration is that customers would like to have a range ofalternative services delivered over the fiber optic lines. It would befeasible to provide the service-specific hardware at the central office,but then all new service-specific hardware must be designed to managethe demarcation point at the opposite end of the access line. In typicalpractice, to provide the service in combination with the conventionalline equipment, service provider service specific equipment is overlaidon the legacy access systems with a new service demarcation pointprovided on the tributary (customer facing) side of that platform. Thisscenario, although currently used due to lack of alternatives, is notpreferred due to significantly higher costs associated with the capitaland operational costs involved (CAPEX & OPEX).

Typical existing access line equipment is analogous to what is usedinside the backbone. Such equipment is operationally rich in features,with comprehensive management capabilities but expensive and complex.Unlike the backbone, however, the fiber optic lines are not used totheir maximum, and the full capabilities of the equipment may end upbeing largely unused, while the customer is left to bear the full costsof this under-utilized infrastructure in the price paid for theservices.

Thus, there is a divergence between the customer's demand foralternative, attractively priced, often state-of-the art services, andoptical service providers' need for higher margins through lower cost,easier to provide and maintain access regardless of the servicesdelivered over them. A solution offered by the disclosed system allowsservices to be defined at the central office, yet allowsservice-agnostic management of access optical fibers and that willprovide infrastructure information and statistics to the serviceproviders in a format easily understood and processed by the OSS andoperational personnel.

Decoupling the management infrastructure from service allows foroptimization of the infrastructure without limiting the servicesdelivered. It is possible to reduce costs and simplify maintenance byproviding service-agnostic management systems.

Easy adaptability of the preferred embodiment OMMS format: fromSONET/SDH, to another, possibly proprietary standard provides anadditional benefit.

FIG. 2 is a schematic diagram of an optical jack networking system. Theterm “optical jack” is used herein to refer to a device for managing,monitoring and analyzing optical facilities. An optical jack located ata customer demarcation point is referred to as a “demarcation jack”herein, while an optical jack located at the service provider centraloffice (CO) is referred to as a “control jack.” It should be understoodthat this terminology is adapted merely for convenience, and does notimply that a type of a demarcation jack described cannot be installed ina service provider's location, or even that such a system is onlyapplicable to customer access lines. The optical jack system may be usedwith any fiber installation, whether completely inside, or crossing theedge of the backbone 50, or in an entirely non-backbone to non-backboneconnection.

The structure of the OMMS and the management information that can bedirectly obtained from processing the received signal or by furtheranalyzing results over time are significant in providing complimentaryoperational value to services being delivered over the optical media. Inthe preferred embodiment of this invention the OMMS is SONET/SDHformatted running at a standard OC-n/STM-n line rate. In addition to thewell known and understood performance monitoring and error detectionprovided over an optical span by Sonet/SDH, other bits of the overheadare available as communication channels to applications at either end.Also significant payload capacity is typically available, againproviding either high bandwidth clear channels or multiple 51 Mbpsindividual channels across the medium. These significant alternativecommunications paths may be used to provide many operationallysupportive applications as outlined in the following figures. A majorbenefit of using a standard optical line protocol is that the linespecific management metrics are provided natively by the linetermination processors, requiring minimal processing before data basing,reducing the protocol processing requirements within the optical jacksallowing the optical jacks to collect, collate and process the raw datawithin the optical jack and provide meaningful management information toeven a local craft interface. Alternative embodiments may use otheroptical line protocols to achieve similar or more specific capabilities.A practitioner of the art will be able to provide many other operatorspecific solutions as required.

As shown in FIG. 2, access loop 120 a may consist of two optical fibers:fiber 202 carrying signals from CO 250 to customer site 110 a, and fiber204 carrying signals in the opposite direction. Control jack 200 mayconsist, among other things, of a multiplexer 210, multiplexing an OMMSonto fiber 202. The OMMS may then be demultiplexed and possiblyprocessed at demarcation jack 230, with the same or a newly formattedOMMS re-multiplexed onto the return fiber 204 to be demultiplexed at thede-multiplex 220 and processed in control jack 200. Analyzing the OMMSprovides an insight into the state of the optical connection. Forexample, the OMMS that has passed through the optical medium may beanalyzed for number of errors, degradation of signal, loss of signal,and other metrics. Such metrics may be those derived from optical lineprotocols such as SONET/SDH or other optical line protocols if utilized,or from measurement and analysis of applications running across the OMMSpayload. If the OMMS reports errors after passing through the opticalmedium, it represents a degraded state of the optical medium itself andsimilar error rates may be inferred for customer channels traveling overthe same medium.

The OMMS is modulated into a wavelength distinct from wavelengths usedby the service, or services, being delivered to the customer. It ismultiplexed using Wave Division Multiplexing (WDM) onto the fiber alongwith wavelengths carrying customer and CO data. In such a way, customerwavelengths remain unaffected, while effective measurement may be madeof the state of the connection. Customer wavelengths may carry variousservices—such as, for example, Gigabit Ethernet, FiberChannel, or video.The management capabilities of the optical jacks are service agnostic inthat no service adaptation is necessary—the services travel overwavelengths natively, not affected by the optical medium managementsignal, traveling on a separate wavelength.

Control jack 200 may communicate with higher order service provider OSSsuch as, for example, with OSS 102, in order to report results ofmanaging, including monitoring and diagnosing, the optical medium. Whilecontrol jack 200 is shown in FIG. 2 to contain both multiplexer 210 anddemultiplexer 220, it should be understood that the presence of both isnot required, and an optical jack may comprise solely a multiplexer ordemultiplexer with any associated management processing. In thepreferred embodiment of the invention, both multiplexers and electronicsfor generating and analyzing optical medium management signals areimplemented in the same hardware, while in an alternative embodiment,they are separate components implemented in hardware and/or software, asdetermined by one skilled in the art.

FIGS. 3 a-b are schematic diagrams of different embodiments ofdemarcation jack 230. In one embodiment of the invention, demarcationjack may consist of an optical jumper connecting the output of thedemultiplexer 220 to the input of the multiplexer 210, decoupling theOMMS from fiber 202 and multiplexing it onto fiber 204. In such a setup, no analysis of the OMMS is performed at the demarcationjack—instead, the control jack receives the OMMS back and performsanalysis of the fiber pair forming an access loop, for example, bycomparing the received OMMS to what was sent out. This is a true passiveset up, with no amplification at the demarcation jack. In this set upthe service provider has management visibility into the integrity of themedium from end to end of an optical loop pair and can detect errors orfaults occurring in either fiber, without the need for additionalequipment. This embodiment of the demarcation jack offers a veryattractive solution in that it may be totally un-powered and requireslittle or no special environmental or security provisions at customerlocations, as typically required for other current methods of providingoptical demarcations.

Illustrated in FIG. 3 b is an alternative embodiment of a demarcationjack 230, containing transceiver 312 and an amplifier 314 configured torepeat a received signal. The demultiplexed OMMS from fiber 202 isdemodulated by transceiver 312 and is then passed to amplifier 314,which amplifies the signal prior to it being re-modulated by thetransceiver and re-multiplexed onto the optical fiber 204. Apractitioner skilled in the art may find this embodiment of theinvention of particular use in long-distance loops where thecapabilities of cost effective transceivers with a limited opticalbudget may be a limitation on the length of optical loops, and using therepeater 3 b may allow for the length of the loop to be increasedsignificantly.

FIG. 4 is a diagram of a single optical fiber connection with activemanagement processing at both ends. Electronic processes have beensimplified to major functional groupings with connectors indicatingrelationships and dependencies. Although indicative of practicalfunctional interrelationships, a practitioner familiar with the art willbe able to envisage many alternative hardware and software solutions toachieve similar functionality. Under control of the system processingand control 418 a the line protocol processing, Sonet/SDH in thepreferred embodiment, is instructed to output an OMMS at a particularsignal rate to the optical transmitter 404. The transmitter 404modulates the OMMS at a particular optical wavelength passing to theoptical multiplexer 210. The multiplexer 210 optically couples the OMMSonto the fiber 202 towards the remote optical jack. At the receivingoptical jack the demultiplexer 220 decouples the OMMS from the fiber 202and passes it to an optical receiver 406. The optical receiverdemodulates the OMMS and passes the resultant electronic signals to thereceive line protocol processing 416. The OMMS line protocol isterminated providing performance and error metrics relative to theoptical medium and providing access to both overhead and payloadcommunications paths between the optical jacks. Management informationis collected from the line protocol processing 416 by the managementinformation processing functions 420 and stored in a local database 528.Information from the local database 528 may be further processed priorto forwarding via the system control 418 b to the EMS/NMS/OSS interface422 for delivery to either a higher order system or OSS for collectionand further processing, or made available to other external craft 424 orintersystem ports 426. Communications paths derived from the OMMS areconnected to the communications processing functions 412 b.Communications paths between communications processes 412 a and 412 bprovide the ability for information to be sent from one end of the fiberto the other.

It should be noted that the direction of the OMMS need not be the sameas the direction of the service signals. For example, it may be usefulto drive a OMMS from the customer site to the service provider site onfiber 202 in order to indicate a fault that has occurred on the opticalservice transmit fiber 204. This counter-directionality may provideadditional diagnostic insight to discover direction-dependent problemswith the optical medium, or may be used to report problems with anoptical medium transmitting an optical service directly to itsassociated transmitting port, thus removing the dependence on a returnpath for management information on another facility from the remote endto indicate problems with the transmit medium. This attribute of thepreferred embodiment is of particular importance to management of singlefiber broadcast services such as analog or digital video transmission.

In addition to managing the connection, optical jack systems may be usedto perform further detailed monitoring by detecting changes in thephysical properties of optical fiber. One of such properties is adependence of bit error rates on received optical power of the signal.An attenuated signal is much more sensitive to changes in physicalproperties of the fiber: such a signal may be used to diagnoseinconsistencies in the fiber which may pose a future problem, and insome implementations provide a methodology to monitor the physicalsecurity of the fiber.

FIG. 15 is a graph of optical power vs. bit error rate of an opticalsignal, expressed in a logarithmic scale. As optical power isattenuated, to lower power levels, bit error rates of the signal risesharply. Normally an optical connection would operate in the range wherebit error rate is sufficiently low, but power requirements are notprohibitively high—the so-called “optical operational envelope”.However, additional analysis may be accomplished by operating themanagement wavelength at the lower power ranges of the optical envelope.Attenuation of the management signal may be achieved by varying thelaunch power of the optical transmitter 404 under the control of thesystem processing and control 418 a or as illustrated in FIG. 4 by theuse of an optical attenuator 402, again under the control of systemprocessing and control.

In the preferred embodiment of the invention, management information isgathered, in particular error rates over time, while operating at apower level within the operational envelope close to the point whereincremental errors would affect the received optical line protocol—forexample, point 1502.

In this mode of operation, with the management channel attenuated to apoint at or near the low power limit of acceptable operation, greatersensitivity to changes in the optical characteristics of the opticalmedium results, and hence the ability of lower speed management signalsto emulate the greater sensitivity to impairments in the optical mediumof services when operated at higher signal rates. When used in thepreferred embodiment, these capabilities of the invention allow lowercost, lower speed optical transmitters, and lower cost, lowersensitivity optical receivers to manage services operating at far higherrates.

In another embodiment, valuable metrics on performance of the medium maybe achieved by “scanning” different optical power levels and detectingand recording the bit error rates of the OMMS after it has passedthrough the optical medium at each of these levels. Recording andprocessing different error rates at different optical power levels mayalso be used in rates of change in the medium and in predicting meantime to failure or other metrics. Scanning may be performedperiodically—for example, every 15 minutes.

In an alternative embodiment of the invention, scanning may be doneconstantly in order to better monitor the fiber. In yet anotherembodiment of the invention, multiple management wavelengths may beused, one used to diagnose normal operating conditions, and another tooperate at attenuated optical power.

Also illustrated in FIG. 4 is forward error control (FEC) encoding 408and decoding 410 processes. As described above, it may be desired tooperate at a point or points within the optical operational envelopewhere increased errors, dependant upon the mode of operation, would bepresent at the receiving line protocol processing. During these periodsof increased errors there is a potential for the protocol processing tobe disrupted to a point where the end to end management signal path islost with the consequential loss of error detection statistics, or thepayload channels used for other applications and reporting could becomeunusable, effectively isolating an optical jack from its partner. FEC408, 410 provides a method for the management signal to be maintainedalong with any associated applications present in the payload whileoperating at a point where errors would normally disrupt suchconnections. While FEC would maintain the connection and recover anyerrors in the management signal, hence masking the error detectioninherent in the optical line protocol, it would also providesupplementary error detection metrics as a result of the FEC decoding410 processes, augmenting the error performance management informationnormally available from the line protocol processing 416.

The correlation of bit error rates vs. received optical power whileoperating at particular wavelengths may be used to provide monitoring ofthe physical security of the fiber. If an intruder attempts to copy thesignal, for example by tapping the optical medium, the received opticalpower level may be affected. During such monitoring, a small change inoptical power may result in a large bit error rate change, thusindicating a change in the attributes of the optical medium requiringinvestigation or action to ensure integrity of the medium.

The optical jack system may be set up to record possible physicalsecurities violations for future analysis, or to pass them to the OSS.In an alternative embodiment of the invention, an optical jack thatdetected physical security violation may affect service-carryingwavelengths by, for example, shutting off signals across that medium, orby inserting a warning message or by inserting a deliberately falsemessage across the medium. A multiplicity of other configurations andapplications are available, as well as understood by one skilled in theart.

In yet other embodiments of the invention, the demarcation jack maycontain additional electronics for analyzing the OMMS or for insertinginto the OMMS management information from the customer site (see FIGS.5-10). As will be apparent to one skilled in the art, the demarcationjack may be implemented as identical to the control jack; these figuresillustrate embodiments of the principals described in FIG. 4 for twofiber networks between two points.

Minor differences exist in the descriptors and connections betweenmanagement processes between FIG. 4 and the following figures. Apractitioner familiar with the art will be able to envisage manyalternative hardware and software solutions to achieve similar requiredfunctionality. Transceiver 516 combines the functions of the opticaltransmitter 404 and optical receiver 406. Transmit logic 518, receivelogic 520 and comparator 522 functions are collectively broadlyanalogous to line protocol processing 414 and 416. Control logic 526 isbroadly analogous to combined system processing and control 418 a and418 b and management information processing 420. Communications logic526 is comparable to communications processing 412 a and 412 b.

FIG. 5 is a diagram of a two fiber loop network connection with apassive demarcation jack. The control jack 20 contains an opticalmultiplexer 514 for multiplexing and de-multiplexing the OMMS onto thefiber, and a transceiver 516 for transmitting and receiving the opticalmedium management signal. Transmitter logic 518 generates a lineprotocol for the optical medium management signal, to be transmitted bytransceiver 516. Transceiver 516 converts the electrical signal from thetransmitter logic 518 at a specified bit rate into a modulated opticalsignal at a specified wavelength (hereinafter referred to as “managementwavelength” to indicate that it carries the optical medium managementsignal) which is then multiplexed with the primary service opticalsignal in the multiplexer 514.

The multiplexed wavelengths traverse the optical access span to thedemarcation jack 230 where multiplexer 504 demultiplexes the managementwavelength, containing the modulated optical medium management signal,from the primary optical signal service. The management wavelength isthen optically looped back through the optical jumper 310 back to themultiplexer 504, which multiplexes it onto fiber 204.

The returned management wavelength is de-multiplexed by multiplexer 514in the control jack 200 and is converted by transceiver 516 from themodulated OMMS into an electric signal. The resulting electrical signalcontaining the returned management protocol is passed on to the receiverlogic 520.

Both transmitter logic and receiver logic pass copies of the protocolsthey, correspondingly, transmit and receive, to comparator 522. Thecomparator 522 identifies differences between transmitted and receivedprotocols (if any), and indicates types and severity of differences tocontrol logic 526. The control logic 526 may decide, based on the errorsit is seeing, to increase or decrease the transmission rate, or tochange the payload, or to send instructions to a receiving optical jack.In addition, information about the error rates and OMMS performance maybe stored in local memory 528, to be later analyzed for possibleprediction of time to failure or for calculation of error-over-time andother trends. Optical jack 200 may communicate with higher order systemlevel electronics, EMS, NMS or OSS through system control port 534. Alocal craft port 532 provides direct technician access to the opticalcontrol jack management information.

In an alternative embodiment of the invention, optical jack 200 need notbe implemented as shown—instead, the different logical processes 518,520, 522, 524, 526, 528, 532 and 534 may be combined into fewer, orseparated into multiple sub processes operating on the same or differentoptical jack. In yet another embodiment of the invention, control logic526 may take on the role of comparing results of the received protocolto the ones received and stored in the database 528 earlier and later intime, in order to perform trend, statistical, probabilistic, or othertypes of analyses.

Meanwhile, it should be understood that communication between serviceprovider transceiver interface 512 and remote transceiver interface 502is in no way impeded by the WDM multiplexed management wavelength, and,in fact, the two transceiver interfaces 502 and 512 may not be aware ofthe overlaying optical jack system.

FIG. 6 is a diagram of an optical loop network with a repeater functionat the demarcation jack. This diagram is similar to what is shown inFIG. 5, with demarcation jack containing a transceiver 312 and anamplifier 314 (as also illustrated in FIG. 3 b). Such a system may beuseful in cases where the distance between the local and remoteassemblies increases the losses of the returned OMMS beyond theoperational specifications of the management signal optical transceiver.

At the demarcation jack the de-multiplexed management wavelength ispassed to the receive optics of transceiver 312, where the modulatedoptical signal is converted to an electrical signal at a resultant bitrate. The resulting electrical signal is amplified in amplifier 314 toappropriate levels and passed to the transmit interface of transceiver312.

Transceiver 312 modulates a specific wavelength with the signal receivedfrom amplifier 314 at a specific bit rate. The resulting repeatedmanagement wavelength is re-multiplexed back to fiber 204 by multiplexer504 to be received and analyzed by control jack 200.

FIG. 7 is a diagram of a two fiber optical loop network connection withmanagement electronics at the demarcation jack. Such a system may beused, for example, to manage loop and optical path integrity. Bycombining the functionality of FIG. 4 on both fibers in oppositedirections, the optical service transmit and receive paths are monitoredindividually in each direction with management information analyzedand/or stored by optical jacks at both ends. In addition, the native oranalyzed results may be exchanged between the optical jacks via thecommunications logic 524 a and 524 b over the communications pathembedded in the optical medium management signal. In addition to passingmanagement information upwards in the network hierarchy towards an OSS,this capability may be further used to store copies of managementinformation databases in physically-redundant locations at each end ofthe facility.

In FIG. 7 and subsequent similar figures, it should be noted thatcomparators 522 a-b do not necessarily compare transmitted protocolswith those received. Instead, they may be comparing the receivedprotocols with those that are expected. Information about what protocolsare expected may come from earlier instruction, or from a particularstandard used or, in fact, from the protocols themselves. In analternative embodiment of the invention, the payload field in a protocolmay contain information about the protocol itself, based on which it maybe able to perform OMMS analysis. In another embodiment of theinvention, analysis of the protocol may be performed based at least inpart on heading and trailing fields of the protocol, which may containerror correction codes. These approaches are particularly useful whenthe multiplexer and demultiplexer are positioned at opposite ends of thefiber.

The control jack 200 may be located at the service provider's side, asdescribed in connection with FIGS. 5-6, while another optical jack of asimilar construction is located at the demarcation point. It will beapparent to one skilled in the art that the demarcation jack may beidentical to the control jack in terms of design and functionalcharacteristics. The difference in roles may be indicated by state ofcontrol interfaces. For example, control jack 200 may have controlinterface 534 enabled, indicating that it is to be the controlling end,while the demarcation jack may lack the control interface. In analternative embodiment of the invention, control and demarcation jacksneed not be the same. For example, control jack 200 may be sub-system ofa larger, more extensive system than customer-site installed demarcationjack 230. Similarly, the processing and analysis performed at each endneed not be the same.

FIG. 8 is a diagram of a two fiber optical loop network connection withremote operational management information interface. The optical jacksystem of this diagram is very similar to that of FIG. 7, with anaddition of customer information management logic 802 at the demarcationjack 230. The customer management information may include anyinformation about a site where the demarcation jack is installed. Forexample, customer information management logic 802 may be connected to apower system and may be able to encode the state of the power system(on/off, low voltage, etc.) or either control or monitor multiple NC/NOcontacts for uses such as remote security or control of remoteenvironmental systems, locally processing and passing managementinformation via the communications facility relative to the variousinterfaces to the associated control jack 200, or directly to higherorder OSS for further processing and action. An alternative embodimentof these capabilities provides similar interfaces on the control jack tocentrally emulate transitions or states of the remotely monitored orcontrolled interfaces. The customer information management logic 802 mayalso include an analog-to-digital converter, converting analog inputs todigital representation, which can be processed by control logic 526 band then, if needed, be transmitted to another optical jack across thecommunications path established as part of the optical medium managementsignal. Such information may be passed directly to the service providermanagement interface for analysis and diagnostics or further processedby the control jack.

One example of use of such local information is in service providerbeing able to correlate information from the optical service status andthe optical jacks to easily distinguish faults in the fiber connectionfrom power failures on the customer end. The customer information is notlimited to power status information—it can include anything andeverything, as deemed necessary by one skilled in the art

Local information management logic may also pass information in theopposite direction: that is, it may pass control and instructions fromthe optical jack to other devices either owned or managed by the serviceproviders such as value added service platforms. The terminology of“customer information” does not imply that such a jack may be onlylocated at the customer site: in fact, local information management maybe accomplished anywhere the optical jack is installed, be it inside oroutside the backbone.

In an alternative embodiment of the invention, there may be more thanone potential connection between each pair of optical jacks. Forexample, in addition to optical connections, there may be a modem orother data communications device connected to the remote craft interfaceproviding remote management access in the event of site isolation. Sucha temporary connection will provide access from either NOC personnel oran automated OSS application to the remote optical demarcation jack. Byreading or querying the remote control logic and/or database, valuablediagnostic management information can be used to facilitate rapidlocalization, repair and recovery from site isolation. The variationsare many and the system may be adapted by one skilled to the art,depending on a particular implementation.

FIG. 9 is a diagram of a two fiber optical loop network connection withmanaged test access points. This set up is very similar to thatdiscussed in connection with previous figures with the ability to switchthe optical medium to external test access points for more comprehensivediagnostic or qualification of the optical medium using optical spectrumanalyzers (OSA), optical time division spectrometers (OTDR) or otherspecialist test or qualification tools available to technicians on siteat optical jack locations. Added in this embodiment of the invention isa set of optical switches 902 a and 902 b to provide test access. Such2×2 optical switches may be software controlled and may be installed atdifferent points on the fiber loop. When activated under the control ofthe local control logic, the optical line may be broken out to testoptical access ports. When both optical switches are activated, thefiber may be un-terminated at both ends and, hence, suitable for OpticalTime Domain Reflectometer (OTDR) access for optical linecharacterization or diagnostics.

If either one of the switches is opened, while the other is maintainednormal, a diagnostic access may be available to primary optical service,and/or OMMS. A message to activate a test access switch may be sent viathe communications path from one optical jack to another. Furthermore,the switching information and the result of the test may be stored in adatabase at either side of the connection.

It may be required that the optical switches be activated for anextended period while testing or characterization is completed. To thisend the control logics 526 a and 526 b may control the switches in anumber of different modes; i) as a latching switch where the unit isrequired to be reset or power cycled to re-establish normal operations;ii) in a non-latching mode wherein the control logic will instruct theswitches to return to their normal state after a fixed period of time,say 5 minutes, and; iii) in a extended non-latching mode wherein theperiod may be programmed under the control of the OSS or a localtechnician. Depending on a protocol agreed upon between two opticaljacks, for each command there may also be a confirming acknowledgementsent back to the originating jack prior to activation of these servicedisruptive tests.

During testing or during interruption in connection, the optical jackson opposite ends of the connection may keep logs of the events, and thenlater, upon reestablishment of the connection, they may synchronize thelogs, or analyze them to determine the cause of the interruption.

FIG. 10 is a diagram of a two fiber optical loop network connection withan optical service monitor.

The demarcation jack 230 includes optical coupler 1002, coupled to fiber202 with a particular coupling ratio determined as part of the serviceoptical budget design to ensure both the primary service and remote OMMSoptical receive power levels are within operational limits. The opticalsignal extracted by remote coupler 1002 is the primary communicationsignal on the line and is connected to optical receiver 1004 of suitablesensitivity, which demodulates the received signal from optical toelectrical data. Remote service monitor 1006 may be a service specificprotocol terminator, such as Gigabit Ethernet, to provide managementinformation such as facility checksum (FCS), loss of signal (LOS) or anyother management information as can be determined from the monitoredservice. In another embodiment the service monitor 1006 may be aconfigurable network processor, which under the control of the OSS maydownload, configure to assume the role of a particular protocolterminator, and provide management information for a range ofalternative services to be monitored.

In an alternative embodiment the service monitor 1006 may simply monitorthe optical power of the optical service, reporting changes or losses tothe control logic 526 b for further processing and reporting to the OSS.

In an alternative embodiment of the invention, service monitor 1006 mayperform security-related functions. In yet another embodiment of theinvention, service monitor 1006 may analyze and record service-specificinformation for billing purposes. The use of service monitor 1006 is notlimited to what is described herein, and it can be adapted to deal withany service-specific monitoring function, as determined by one skilledin the art.

In an alternative embodiment of the invention, one of the optical jackson a loop may perform a service emulator function. A service emulatormay be used to reduce the alarm severity of an optical service portwhere one of the ends of the service is not yet commissioned or there isan interruption in connection for some reason. For example, when anoptical line is provisioned, it may happen that the customer does notreceive customer-side equipment for some time, while the serviceprovider's side has already been activated. The lack of connection fromthe customer side may result in a port alarm on the service interface512 in the providers CO. These alarms, although important in day to dayoperation indicating failures in connected facilities, are viewed asunimportant while a service is being commissioned. Unfortunately thereis no method of determining whether a port alarm is as a result of afailure in a facility or as a result of an un-terminated service at thecustomer location, typically requiring additional effort to eitheracknowledge or disable this nuisance alarm. Depending on a particularOSS, diagnosing this predictable alarm may take time and resources fromother tasks; therefore, it would be useful to have a way of simulatingthe connection while the customer side is not active. Service emulatoracts as such a simulator, placing the service port in loopback whenevera loss of signal is detected on the incoming fiber 204.

As discussed above, the use of optical jacks is not limited tocustomer-service provider connections. They may be implemented insideand outside of the backbone, in any number of network topologies: mesh,complex mesh, spur, extended spur, ring, hub, etc. FIG. 11 is aschematic diagram of one network topology, where optical jacks 200 a-xmanage different optical connection loops. The optical jacks may be incommunication with each other via the inter-system port 426, extendingthe management and control plane across multiple optical jacks, and alsowith management interface 1102, reporting to it management information,and receiving instructions and data for transmission to other opticaljacks.

In the preferred embodiment, optical jacks to support topologies morecomplex than simple spurs may be physically combined to provide supportfor two or more, one or two fiber network spans with consolidatedelectronic processing collectively supporting all individual connectionsmanaged by the optical jack. Furthermore, the jacks may be capable ofautomatically discovering additional optical jacks on paths connected toa given point, extending the management and control plane, establishinga network of optical jacks that are aware of each other and that canwork in a collaborative mode to route traffic and manage opticalconnections. Service channels on managed optical connections are notlimited to a particular standard or a waveband. For example, they can bein the 850 nm, 1200 nm-1400 nm, 1470 nm-1610 nm, or other wavebands. Inone embodiment of the invention, a management wavelength may be selectedto fall into a different waveband than data-carrying service wavebands:such a set up eases optical multiplexing and de-multiplexingspecifications, and might allow for use of less-precise, and, thus, lessexpensive components. In an alternative embodiment of the invention,however, the management wavelength may be chosen to fall into the samewaveband as the service-carrying wavelength, in order to better diagnosethe real conditions experienced by the service-carrying wavelengths inthat waveband.

The management wavelength may be pre-selected prior to a particularoptical jack being put into use. Alternatively, it may be set some timeduring the operation, or even be changed from time to time during theoperation of the optical jack. In yet another embodiment of theinvention, a management wavelength may be determined automaticallyduring the operation of the optical jack. FIG. 12 is a diagram ofoptical a two fiber loop network connection with tunable opticalcomponents, allowing for dynamic modification of management wavelength.

The tunable optical management wavelength capability is provided throughthe use of tunable transceivers 1214 and tunable optical multiplexer's1212 a-b. Tunable transceivers 1214 a-b and multiplexers 1212 a-b may betuned to a pre-selected wavelength during commissioning of an opticaljack, or at maintenance time. Such pre-selected wavelength may beoutside of the range of the configured primary service waveband.

The configuration of the tuned management wavelength may be stored in adatabase as part of the assembly configuration, facilitating recovery ofthe management wavelength and associated communications following arestart or a failure.

In an alternative embodiment of the invention, optical jacks withtunable transceivers and multiplexers may be further equipped with logicfor automatically picking a particular wavelength to use as a managementwavelength. Furthermore, such wavelength may be changed based oninstructions from another optical jack, or based on local conditions.

An application of tunable management wavelengths may be in ensuringproper service for service-carrying wavelengths: for example, if thesignal seems to go through on some channels, but not on others, tunableoptical jacks may be able to set management wavelength to one of thefaulty channels or nearby channels and test various configurations todetermine the point of failure. In yet another embodiment of theinvention, the management wavelength may be changed in case of a severedegradation of service in a particular waveband, to deliver a warning offailure to the management operations.

It may be noted that a great number of wavelengths may be multiplexedonto a single fiber, thus increasing carrying capacity. FIGS. 13 a-13 bare schematic representations of wave division multiplexing. Opticalmultiplexer 210 may not only multiplex the OMMS onto the fiber, but alsomultiplex service-carrying wavelengths onto the same fiber, as shown inFIG. 13 a. In another embodiment of the invention, service-carryingwavelengths may already be multiplexed together by a separatemultiplexer 1302, and optical multiplexer 210 inside optical jack 200may only need to multiplex the OMMS onto the already-WDM-multiplexedconnection, as shown in FIG. 13 b.

In yet another embodiment of the invention, there may be more than oneoptical medium management signals. Different signals may be separatedbased on functionality, or based on their wavelengths falling intodifferent wavebands. By providing multiple management wavelengths, anoptical jack system may provide additional management, services andmonitoring capabilities, as determined by one skilled in the art.

Optical jack systems may be used as part of central office operations,providing management of customer accesses and connections to othercentral offices. FIG. 14 is a diagram of an optical jack networkingsystem. Patch panel optical distribution frame (ODF) 1402, one or moreof which, provide interconnection points between the optical serviceinterface and the fiber distribution external plant (Cable Head End) tocustomer sites, may be made up, for example, of multiple optical jacks200 a-x mounted in a high density system and corresponding managementmechanisms, managing connections to demarcation jacks 230 a-x. In thispreferred embodiment such a system would be the initial ODF/patch paneladjacent to the optical service interface, connected to the port by ashort patch cord. In such a way, optical service provider 512 may beable to manage various connections, using technology similar in formfactor to what is currently existing while extending the managementvisibility of the optical media 202 and 204 from the optical interface512 across and through any other interconnection frames all the way tothe remote optical demarcation jack 230. As will be recognized by oneskilled in the art, optical jacks in such a set up may be implemented ascards that can be inserted into racks making up an ODF. As connectionsare added, additional cards may be inserted into rack slots, creating amodular optical management system.

An alternative embodiment may consist of the control jack 200 being asubsystem embedded in the optical service interface port 512 with themanagement and control plane tightly integrated into the operatingsystem of the major system.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

1. A telecommunications system comprising: an optical medium betweenservice provider equipment and a demarcation point, the service providerequipment providing service signals of one or more optical wavelengthson the optical medium toward customer line equipment coupled to thedemarcation point; an optical transmitter providing a management signalon a wavelength separate from the service wavelengths; an opticalmultiplexer that multiplexes the management signal onto the opticalmedium; an optical demultiplexer that demultiplexes the managementsignal after the management signal has passed through the opticalmedium; and electronics for processing the demultiplexed managementsignal and providing management information based on the processing, themanagement information indicating a state of the optical mediumindependent of a state of the customer line equipment.
 2. The system ofclaim 1, wherein the management signal is formatted with an optical lineprotocol structured for error detection.
 3. The system of claim 2,wherein changes in error rates indicate changes in state of the opticalmedium.
 4. The system of claim 1, wherein the management signal isformatted with an optical line protocol structured to have at least onemonitoring overhead field and at least one payload field.
 5. The systemof claim 1, wherein the electronics store the management information toa database.
 6. An apparatus for customer access of a telecommunicationsnetwork, comprising: an optical medium at an edge of the network betweenservice provider equipment and a demarcation point, the service providerequipment providing customer service signals of one or more opticalwavelengths on the optical medium to the demarcation point; an opticaltransmitter providing a management signal on a wavelength separate fromthe service wavelengths, the management signal formatted with an opticalline protocol structured to have at least one error detection overheadfield and at least one payload field; an optical multiplexer on theservice provider side of the demarcation point which multiplexes themanagement signal onto the optical medium; an optical demultiplexer onthe service provider side of the demarcation point which demultiplexesthe management signal after the management signal has passed through theoptical medium; and electronics that process the demultiplexedmanagement signal and provide management information based on theprocessing, the management information indicating a state of the opticalmedium independent of a state of the customer line equipment.
 7. Theapparatus of claim 6, wherein the management signal is transmitted atone or more levels where the received management signal is sensitive tochanges in state of the optical medium.
 8. The apparatus of claim 7,wherein the received management signal is sensitive to changes in stateof the optical medium relative to the service signals.
 9. The apparatusof claim 6, wherein the management signal is transmitted at asensitivity level resulting in errors in the demultiplexed managementsignal.
 10. The apparatus of claim 9, wherein the management signal istransmitted at a level that varies over time.
 11. The apparatus of claim10, wherein the electronics process the demultiplexed management signalto determine error rates of the management signal corresponding todifferent transmit levels.
 12. An optical jack for providing managementinformation relative to an optical medium carrying service signals ofone or more wavelengths, the jack comprising: an optical transmittermodulating a management signal at a wavelength distinct from the servicewavelengths, the management signal being formatted with an optical lineprotocol structured for error detection; an optical multiplexer whichmultiplexes the transmitted management signal onto the optical medium;an optical demultiplexer which demultiplexes a received managementsignal after the management signal has passed through the opticalmedium; an optical receiver demodulating the received management signal;and electronics that process the demodulated received management signalto provide management information relative to the optical medium usingerror rates in the received management signal.
 13. The optical jack ofclaim 12, wherein the optical line protocol is structured to include atleast one payload field and at least one overhead monitoring field. 14.The optical jack of claim 13, wherein the payload field comprisescontrol information for a second optical jack.